The present invention generally relates to methods for fabricating compound material wafers. An embodiment includes providing a donor substrate, forming a weakened zone in the donor substrate to define a transfer layer, bonding the surface of the transfer layer to a handle substrate, and detaching the donor substrate at the weakened zone to transfer the transfer layer onto the handle substrate. This forms a compound material wafer, and the transfer layer detached donor wafer provides a remainder substrate having a surface where the transfer layer was detached. Next, an additional layer is deposited onto a surface of the remainder substrate to increase its thickness and to form a reconditioned substrate, and the reconditioned substrate is recycled as a donor substrate for fabricating additional compound material wafers.
Published U.S. application no. 2003/0153163 describes a method for transferring a layer of material from a donor substrate to a handle substrate using the SMART-CUT® technology. The method includes forming a donor substrate by bonding a first wafer having a transfer layer to a support substrate. U.S. application no. 2003/0153163 discloses that it is advantageous to form such a donor wafer for transferring layers of expensive material because it allows for repeated use of the transfer operation from the same initial first wafer, until that wafer is too thin to proceed again.
There are several drawbacks to this known method. Due to the fact that the donor substrate is composed of two wafers bonded together, the donor wafer thickness, in particular for the first few transfers, is typically much larger than the thickness of donor wafers used in standard processes. For example, such a donor substrate is thicker than that typically used in the SMART-CUT® technology process for producing silicon on insulator wafers. Accordingly, the equipment used for handling and supporting the donor wafers during the transfer process has to be specially adapted to the increased weight and thickness, or else the support substrate has to be specially reduced in thickness. Both of these solutions, however, require adaptive steps which are very costly. In addition, during the manufacturing process, the thickness of the donor wafer varies, and the extent of the variation depends on the number of transfers performed. As a consequence, the processing and handling equipment needs to be specially designed to cope with the varying conditions. Such specially designed equipment adds more expense to the process.